1. Field of the Invention:
This invention relates generally to digital-to-analog converters and, more specifically, to a digital-to-analog current source cell having a switching means that reduces the dynamic power consumed during times of activity.
2. Description of the Prior Art:
Under current designs, when a digital-to-analog (DA) current steering matrix is active, the current sources are always operational. The output from the current sources is steered to ground or to an output depending on what portion of the current steering matrix is enabled by a control signal (CE). In order to reduce the static power consumed by the current steering matrix, prior art designs implemented a sleep mode during times of matrix inactivity. During the sleep mode, a bias signal, which controls the magnitude of the current from the current source, is shut off, thereby effectively turning off the current source. This reduces the static power consumed by the matrix during times of inactivity. The problem with this solution is that during operation there is a significant amount of power being needlessly dissipated to ground.
Therefore, a need existed to provide an improved DA current source cell. The improved current source cell must produce the same output characteristics as prior art current source cells, yet with the ability to dynamically control the output current to the current steering matrix. This will reduce the power dissipation of the matrix during times of matrix activity without effecting the digital-to-analog function of the circuit.